For crosslinking a fluorine-containing polymer, particularly a fluorine-containing elastomer, usual crosslinking methods are polyamine vulcanization, polyol vulcanization and organic peroxide vulcanization. In any of those methods, high temperature is necessary in order to obtain a crosslinked article and therefore application thereof is limited.
Particularly in case of a method of crosslinking a fluorine-containing elastomer having iodine or bromine, generally a method of crosslinking with an organic peroxide is employed. However the crosslinking needs to be carried out at high temperature and in case of usual molding, a crosslinking reaction does not proceed in the neighborhood of an interface with oxygen and staining of a metal die arises. Thus there is a problem with processability.
JP-B-5-63482, etc. describe crosslinking methods other than the method of crosslinking by using heat energy, namely methods of crosslinking by using radiation, etc. Such methods require expensive facilities and are not carried out easily and therefore application thereof is limited to only particular fields.
For example, in crosslinking of a fluorine-containing polymer, ionizing radiation, etc. have been adopted practically for crosslinking of a tetrafluoroethylene-ethylene copolymer (ETFE), polyvinylidene fluoride (PVdF), and the like, but only in the field of electric cables. As for perfluoropolymers, it is assumed that crosslinking thereof is still difficult.
On the other hand, urethane rubber and silicone rubber are on the market and are widely used because crosslinking need not be carried out at high temperature and can be carried out at room temperature. However the urethane rubber has a problem with heat resistance and water resistance, and the silicone rubber has a problem with chemical resistance and oil resistance.
As mentioned above, there have been no fluorine-containing polymer compositions which could be cured at room temperature while maintaining excellent properties of the fluorine-containing polymer.
An object of the present invention is to provide a crosslinkable composition comprising a polymer containing iodine and/or bromine in a specific amount, particularly an ultraviolet-crosslinkable fluorine-containing polymer, and also to provide a crosslinked article obtained from the composition.